For a multilayer substrate with one or more ground planes and single-ended signal distribution, as is typical at millimeter wave frequencies, patch antennas are used for easy integration with radio frequency integrated circuits (RFICs). While patch antennas are efficient in terms of radiation and only require a single-ended feed, they radiate mainly in the plane normal to the substrate. This radiation direction makes it difficult for mounting the substrate on a chassis of a typical consumer electronic product where the radiation comes out only in a direction parallel to the substrate. To overcome this problem, end-fire antennas are used which can radiate predominantly towards the edge of the antenna. The most common type of end-fire antenna with end-fire radiation is a planar dipole antenna.
However, the integration of a conventional planar dipole antenna in a multi-layer substrate is challenging because the need for balanced feed to the conventional planar dipole antenna and removal of ground planes near the conventional planar dipole antenna make the total size of the antenna quite large. Moreover, the large sized conventional planar dipole antennas, when packed in array topologies with driving RFICs in the same package on a common substrate, are challenging because of the large size to integrate within consumer electronic devices which are becoming smaller in size.